Resist composition and method for producing resist pattern

ABSTRACT

A resist composition having a resin having a structural unit represented by the formula (I), a resin being insoluble or poorly soluble in alkali aqueous solution, but becoming soluble in an alkali aqueous solution by the action of an acid and not including the structural unit represented by the formula (I), and an acid generator, 
     
       
         
         
             
             
         
       
         
         
           
             wherein R 1 , A 1 , R 2 , R b1 , R b2 , L b1 , ring W b1 , R b3 , R b4 , and Z1 +  are defined in the specification.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2011-157521filed on Jul. 19, 2011. The entire disclosures of Japanese ApplicationNo. 2011-157521 is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist composition and a method forproducing a resist pattern.

2. Background Information

A resist composition which contains a resin including a polymer having astructural unit (u-A) and a structural unit (u-B), and a polymer havinga structural unit (u-B), a structural unit (u-C) and a structural unit(u-D), and an acid generator, is described in Patent document ofJP-2010-197413A.

However, with the conventional resist composition, the exposure margin(EL) at producing a resist pattern may be not always satisfied with.

SUMMARY OF THE INVENTION

The present invention provides following inventions of <1> to <7>.

<1> A resist composition comprising

a resin having a structural unit represented by the formula (I),

a resin being insoluble or poorly soluble in alkali aqueous solution,but becoming soluble in an alkali aqueous solution by the action of anacid and not including the structural unit represented by the formula(I), and

an acid generator represented by the formula (II),

wherein R¹ represents a hydrogen atom or a methyl group;

A¹ represents a C₁ to C₆ alkanediyl group;

R² represents a C₁ to C₁₀ hydrocarbon group having a fluorine atom;

wherein R^(b1) and R^(b2) independently represent a fluorine atom or aC₁ to C₆ perfluoroalkyl group;

L^(b1) represents a C₁ to C₁₇ divalent saturated hydrocarbon group, oneor more —CH₂— contained in the saturated hydrocarbon group may bereplaced by —O— or —CO—;

ring W^(b1) represents a C₂ to C₃₆ heterocycle;

R^(b3) represents a hydrogen atom or a C₁ to C₁₂ hydrocarbon group, oneor more —CH₂— contained in the hydrocarbon group may be replaced by —O—or —CO—;

R^(b4) in each occurrence independently represent a C₁ to C₆ hydrocarbongroup, one or more —CH₂— contained in the hydrocarbon group may bereplaced by —O— or —CO—;

m represents an integer of 0 to 6; and

Z¹⁺ represents an organic cation.

<2> The resist composition according to <1>, wherein A¹ in the formula(I) is an ethylene group.

<3> The resist composition according to <1> or <2>, wherein R² in theformula (I) is a C₁ to C₆ fluorinated alkyl group.

<4> The resist composition according to any one of <1> to <3>, whereinL^(b1) is a group represented by formula (L1-1)

wherein L^(b2) represents a single bond or a C₁ to C₁₅ saturatedhydrocarbon group and

* represent a bond to the carbon atom of —C(R^(b1))(R^(b2))—.

<5> The resist composition according to any one of <1> to <4>, whereinZ¹⁺ is a triaryl sulfonium cation.

<6> The resist composition according to any one of <1> to <5>, whichfurther comprises a solvent.

<7> A method for producing a resist pattern comprising steps of;

(1) applying the resist composition of any one of <1> to <5> onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the chemical structure formulas of the present specification, unlessotherwise specified, the suitable choice of carbon number made for theexemplified substituent groups are applicable in all of the chemicalstructure formulas that have those same substituent groups. Unlessotherwise specified, these can include any of straight-chain, branchedchain, cyclic structure and a combination thereof. When there is astereoisomeric form, all stereoisomeric forms included.

“(Meth)acrylic monomer” means at least one monomer having a structure of“CH₂═CH—CO—” or “CH₂═C(CH₃)—CO—”, as well as “(meth)acrylate” and“(meth)acrylic acid” mean “at least one acrylate or methacrylate” and“at least one acrylic acid or methacrylic acid,” respectively.

<Resist Composition>

The resist composition of the present invention contains;

a resin (hereinafter may be referred to as “resin (A)”), and

an acid generator represented by the formula (II) (hereinafter may bereferred to as “acid generator (II)”).

Further, the present resist composition preferably contains a solvent(hereinafter may be referred to as “solvent (E)”) and/or an additivesuch as a basic compound (hereinafter may be referred to as “basiccompound (C)”) which is known as a quencher in this technical field, asneeded.

<Resin (A)>

The resin (A) includes;

a resin having a structural unit represented by the formula (I)(hereinafter is sometimes referred to as “resin (A1)”), and

a resin being insoluble or poorly soluble in alkali aqueous solution,but becoming soluble in an alkali aqueous solution by the action of anacid and not including the structural unit represented by the formula(I) (hereinafter is sometimes referred to as “resin (A2)”).

Also, the resin (A) may contain a structural unit other than the resin(A1) and resin (A2).

<Resin (A1)>

The resin (A1) has a structural unit represented by the formula (I)(hereinafter may be referred to as “structural unit (I)”).

wherein R¹ represents a hydrogen atom or a methyl group;

A¹ represents a C₁ to C₆ alkanediyl group;

R² represents a C₁ to C₁₀ hydrocarbon group having a fluorine atom;

In the formula (I), examples of the alkanediyl group of A¹ include achain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl; abranched alkanediyl group such as 1-methylpropane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl,1-methylbutane-1,4-diyl, 2-methylbutane-1,4-diyl groups.

The hydrocarbon group of R² may be any of an aliphatic hydrocarbongroup, an aromatic hydrocarbon group and a combination of two or moresuch groups. The aliphatic hydrocarbon group may be any of a chain andcyclic aliphatic hydrocarbon group, and a combination of two or moresuch groups. The aliphatic hydrocarbon group may include a carbon-carbondouble bond, and is preferably a saturated aliphatic hydrocarbon group,i.e., an alkyl group and an alicyclic hydrocarbon group.

Examples of the alkyl group include methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, tert-butyl, iso-butyl, n-pentyl, iso-pentyl,tert-pentyl, neo-pentyl, hexyl, octyl and 2-ethylhexyl groups.

The alicyclic hydrocarbon group may be either monocyclic or polycyclichydrocarbon group. Examples of the monocyclic alicyclic hydrocarbongroup include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl, cyclooctyl and cyclodecyl groups. Examples of thepolycyclic alicyclic hydrocarbon group include decahydronaphtyl,adamantyl, 2-alkyladamantane-2-yl, 1-(adamantane-1-yl)alkane-1-yl,norbornyl, methylnorbornyl and isobornyl groups.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

The hydrocarbon group having a fluorine atom of R² is preferably analkyl group having a fluorine atom and an alicyclic hydrocarbon grouphaving a fluorine atom.

Examples of the alkyl group having a fluorine atom include a fluorinatedalkyl group such as difluoromethyl, trifluoromethyl, 1,1-difluoroethyl,2,2-difluoroethyl, 1,1,1-trifluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl,perfluoroethylmethyl, 1-(trifluoromethyl)-1,2,2,2-tetratrifluoroethyl,perfluoropropyl, 1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl, perfluoropentyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl, perfluoropentylmethyl,perfluorohexyl, perfluoroheptyl and perfluorooctyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluocyclohexyl andperfluoroadamantyl groups.

A¹ in the formula (I) is preferably a C₂ to C₄ alkanediyl group, andmore preferably an ethylene group.

R² is preferably a fluorinated alkyl group, and more preferably a C₁ toC₆ fluorinated alkyl group.

Specific examples of the structural units (I) include as follows.

Also, examples of the structural units (I) include structural units inwhich a methyl group corresponding to R¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

The structural unit (I) is derived from a compound represented by theformula (I′), hereinafter may be referred to as “compound (I′)”.

wherein A¹, R¹ and R² have the same definition of the above.

The compound (I′) can be produced by a method below.

wherein A¹, R¹ and R² have the same definition of the above.

The compound (I′) can be obtained by reacting a compound represented bythe formula (1′-1) with a compound represented by the formula (I′-2) inpresence of a basic catalyst in a solvent. Preferred examples of thebasic catalyst include pyridine. Preferred examples of the solventinclude tetrahydrofuran.

As the compound represented by the formula (I′-1), a marketed productmay be used. The hydroxyethyl methacrylate can be used as a marketedproduct.

The compound represented by the formula (I′-2) can be obtained byconverting corresponding carboxylic acid, depending on the kinds of R²,into an anhydride. The heptafluoro butyric anhydride can be used as amarketed product.

The resin (A1) may include a structural unit other than the structuralunit (I).

Examples of the structural unit other than the structural unit (I)include a structural unit derived from a monomer having an acid labilegroup described below (hereinafter may be referred to as “-acid labilemonomer (a1)”), a structural unit derived from a monomer not having anacid labile group described below (hereinafter may be referred to as“-acid stable monomer”), a structural unit derived from a known monomerin this field, a structural unit represented by the formula (IIIA)described below (hereinafter is sometimes referred to as “structuralunit (IIIA)”). Among these, the structural unit (IIIA) is preferable.

wherein R¹¹ represents a hydrogen atom or a methyl group;

ring W² represents a C₆ to C₁₀ hydrocarbon ring;

A¹² represents —O—, *—CO—O— or * —O—CO—, * represents a bond to ring W²;

R¹² represents a C₁ to C₆ alkyl group having a fluorine atom.

The hydrocarbon ring of the ring W² may be an alicyclic hydrocarbonring, and preferably a saturated alicyclic hydrocarbon ring.

Examples of the saturated aliphatic hydrocarbon ring include a ringbelow.

As the ring W², an adamantane ring and cyclohexane ring are preferable,and an adamantane ring is more preferable.

Examples of the alkyl group having a fluorine atom of the R¹² include afluorinated alkyl group such as, groups described below, difluoromethyl,trifluoromethyl, 1,1-difluoroethyl, 2,2-difluoroethyl,2,2,2-trifluoroethyl, perfluoroethyl, 1,1,2,2-tetrafluoropropyl,1,1,2,2,3,3-hexafluoropropyl, perfluoro ethylmethyl,1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl, perfluoropropyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl, perfluoropentyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl, perfluoro pentylmethyl andperfluorohexyl groups.

Examples of the structural unit represented by the formula (IIIA)include structural units below.

Also, examples of the structural units (IIIA) include structural unitsin which a methyl group corresponding to R¹¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

Among these, the structural unit (IIIA-1) and the structural unit(IIIA-1) in which a methyl group corresponding to R¹¹ in the structuralunit (IIIA-1) represented by the above is replaced by a hydrogen atomare preferable.

The proportion of the structural unit (I) in the resin (A1) is generally5 to 100 mol %, preferably 10 to 100 mol %, more preferably 50 to 100mol %, still more preferably 80 to 100 mol %, and, in particular,preferably almost 100 mol %, with respect to the total structural units(100 mol %) constituting the resin (A1).

Within the proportion of the structural unit (I), it is possible toproduce a resist pattern with defect-free.

When the resin (A1) contains the structural unit (MA), the proportionthereof in the resin (A1) is generally 1 to 95 mol %, preferably 2 to 80mol %, more preferably 5 to 70 mol %, still more preferably 5 to 50 mol% and in particular preferably 5 to 30 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A1).

For achieving the proportion of the structural unit (I) and/or thestructural unit (IIIA) in the resin (A1) within the above range, theamount of the compound (I′) and/or a monomer giving the structural unit(IIIA) to be used can be adjusted with respect to the total amount ofthe monomer to be used when the resin (A1) is produced (the same shallapply hereinafter for corresponding adjustment of the proportion).

The resin (A1) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of thecompound (I′) and/or at least one of the monomer giving the structuralunit (IIIA), and optionally at least one of the acid labile monomer(a1), at least one of the acid stable monomer and/or at least one of aknown compound.

The weight average molecular weight of the resin (A) is preferably 5,000or more (more preferably 7,000 or more, and still more preferably 10,000or more), and 80,000 or less (more preferably 50,000 or less, and stillmore preferably 30,000 or less).

The weight average molecular weight is a value determined by gelpermeation chromatography using polystyrene as the standard product. Thedetailed condition of this analysis is described in Examples.

<Resin (A2)>

The resin (A2) is a resin having properties which is insoluble or poorlysoluble in alkali aqueous solution, but becomes soluble in an alkaliaqueous solution by the action of an acid. Here “a resin becomingsoluble in an alkali aqueous solution by the action of an acid” means aresin that has an acid labile group and is insoluble or poorly solublein aqueous alkali solution before contact with the acid, and becomessoluble in aqueous alkali solution after contact with an acid.

Therefore, the resin (A2) is preferably a resin having at least onestructural unit derived from an acid labile monomer (a1).

Also, the resin (A2) may include a structural unit other than thestructural unit having the acid labile group as long as the resin (A2)has above properties and does not have the structural unit (I).

Examples of the structural unit other than the structural unit havingthe acid labile group include a structural unit derived from the acidstable monomer, the structural unit derived from a known monomer in thisfield, the structural units represented by the formula (IIIA) describedabove.

<Acid Labile Monomer (a1)>

The “acid labile group” means a group which has an elimination group andin which the elimination group is detached by contacting with an acidresulting in forming a hydrophilic group such as a hydroxy or carboxygroup. Examples of the acid labile group include a group represented bythe formula (I) and a group represented by the formula (2). Hereinaftera group represented by the formula (I) may refer to as an “acid labilegroup (1)”, and a group represented by the formula (2) may refer to asan “acid labile group (2)”.

wherein R^(a1) to R^(a3) independently represent a C₁ to C₈ alkyl groupor a C₃ to C₂₀ alicyclic hydrocarbon group, or R^(a1) and R^(a2) may bebonded together to form a C₂ to C₂₀ divalent hydrocarbon group, *represents a bond. In particular, the bond here represents a bondingsite (the similar shall apply hereinafter for “bond”).

wherein R^(a1)′ and R^(a2)′ independently represent a hydrogen atom or aC₁ to C₁₂ hydrocarbon group, R^(a3)′ represents a C₁ to C₂₀ hydrocarbongroup, or R^(a2)′ and R^(a3)′ may be bonded together to form a divalentC₂ to C₂₀ hydrocarbon group, and one or more —CH₂— contained in thehydrocarbon group or the divalent hydrocarbon group may be replaced by—O— or —S—, * represents a bond.

Examples of the alkyl group of R^(a1) to R^(a3) include methyl, ethyl,propyl, butyl, pentyl and hexyl groups.

Examples of the alkyl group of R^(a1) to R^(a3) include methyl, ethyl,propyl, butyl, pentyl and hexyl groups.

Examples of the alicyclic hydrocarbon group of R^(a1) to R^(a3) includemonocyclic hydrocarbon groups such as a cycloalkyl group, i.e.,cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl,cycloheptyl, cyclooctyl groups; and polycyclic hydrocarbon groups suchas decahydronaphtyl, adamantyl, norbornyl (i.e., bicyclo[2.2.1]heptyl),and methyl norbornyl groups as well as groups below.

The hydrogen atom contained in the alicyclic hydrocarbon group of R^(a1)to R^(a3) may be replaced an alkyl group. In this case, the carbonnumber of the alicyclic hydrocarbon group is comparable to the totalcarbon number of the alkyl group and the alicyclic hydrocarbon group.

The alicyclic hydrocarbon group of R^(a1) to R^(a3) preferably has 3 to16 carbon atoms, and more preferably has 4 to 16 carbon atoms.

When R^(a1) and R^(a2) is bonded together to form a C₂ to C₂₀hydrocarbon group, examples of the group-C(R^(a1))(R^(a2))(R^(a3))include groups below. The divalent hydrocarbon group preferably has 3 to12 carbon atoms. * represents a bond to —O—.

Specific examples of the acid labile group (1) include, for example,

1,1-dialkylalkoxycarbonyl group (a group in which R^(a1) to R^(a3) arealkyl groups, preferably tert-butoxycarbonyl group, in the formula (1)),2-alkyladamantane-2-yloxycarbonyl group (a group in which R^(a1), R^(a2)and a carbon atom form adamantyl group, and R^(a3) is alkyl group, inthe formula (I)), and 1-(adamantane-1-yl)-1-alkylalkoxycarbonyl group (agroup in which R^(a1) and R^(a2) are alkyl group, and R^(a3) isadamantyl group, in the formula (I)).

The hydrocarbon group of R^(a1)′ to R^(a3)′ includes any of an alkylgroup, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the divalent hydrocarbon group which is formed by bondingwith R^(a2)′ and R^(a3)′ include a divalent aliphatic hydrocarbon group.

At least one of R^(a1)′ and R^(a2)′ is preferably a hydrogen atom.

Specific examples of the acid labile group (2) include a group below.

The acid labile monomer (a1) is preferably a monomer having an acidlabile group and a carbon-carbon double bond, and more preferably a(meth)acrylic monomer having the acid labile group.

Among the (meth)acrylic monomer having an acid labile group, it ispreferably a monomer having a C₅ to C₂₀ alicyclic hydrocarbon group.When a resin which can be obtained by polymerizing monomers having bulkystructure such as the alicyclic hydrocarbon group is used, the resistcomposition having excellent resolution tends to be obtained during theproduction of a resist pattern.

Examples of the (meth)acrylic monomer having the acid labile group (1)and a carbon-carbon double bond preferably include a monomer representedby the formula (a1-1) and a monomer represented by the formula (a1-2),below (hereinafter are sometimes referred to as a “monomer (a1-1)” and a“monomer (a1-2)”). These may be used as a single monomer or as acombination of two or more monomers.

wherein L^(a1) and L^(a2) independently represent *—O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group;

R^(a4) and R^(a5) independently represent a hydrogen atom or a methylgroup;

R^(a6) and R^(a7) independently represent a C₁ to C₈ alkyl group or a C₃to C₁₀ alicyclic hydrocarbon group;

m1 represents an integer 0 to 14;

n1 represents an integer 0 to 10; and

-   -   n1′ represents an integer 0 to 3.

In the formula (a1-1) and the formula (a1-2), L^(a1) and L^(a2) arepreferably *—O— or *—O—(CH₂)_(k1′)—CO—O—, here k1′ represents an integerof 1 to 4 and more preferably 1, and more preferably *—O.

R^(a4) and R^(a5) are preferably a methyl group.

Examples of the alkyl group of R^(a6) and R^(a7) include methyl, ethyl,propyl, butyl, pentyl, hexyl and octyl groups. Among these, the alkylgroup of R^(a6) and R^(a7) is preferably a C₁ to C₆ alkyl group.

Examples of the alicyclic hydrocarbon group of R^(a6) and R^(a7) includemonocyclic hydrocarbon groups such as cyclopentyl, cyclohexyl,methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl groups;and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl,norbornyl (i.e., bicyclo[2.2.1]heptyl), and methyl norbornyl groups aswell as groups above. Among these, the alicyclic hydrocarbon group ofR^(a6) and R^(a7) is preferably a C₃ to C₈ alicyclic hydrocarbon group,and more preferably a C₃ to C₆ alicyclic hydrocarbon group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1∝ is preferably 0 or 1, and more preferably 1.

Examples of the monomer (a 1-1) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a1-1-1) to the formula (a 1-1-8), and morepreferably monomers represented by the formula (a 1-1-1) to the formula(a 1-1-4) below.

Examples of the monomer (a1-2) include 1-ethyl-1-cyclopentane-1-yl(meth)acrylate, 1-ethyl-1-cyclohexane-1-yl (meth)acrylate,1-ethyl-1-cycloheptane-1-yl (meth)acrylate, 1-methyl-1-cyclopentane-1-yl(meth)acrylate and 1-isopropyl-1-cyclopentane-1-yl (meth)acrylate. Amongthese, the monomers are preferably monomers represented by the formula(a1-2-1) to the formula (a1-2-12), and more preferably monomersrepresented by the formula (a1-2-3), the formula (a1-2-4), the formula(a1-2-9) and the formula (a1-2-10), and still more preferably monomersrepresented by the formula (a1-2-3) and the formula (a1-2-9) below.

When the resin (A2) contains the structural unit (a1-1) and/or thestructural unit (a1-2), the total proportion thereof is generally 10 to95 mol %, preferably 15 to 90 mol %, more preferably 20 to 85 mol %,with respect to the total structural units (100 mol %) of the resin(A2).

Examples of a monomer having an acid-labile group (2) and acarbon-carbon double bond include a monomer represented by the formula(a1-5). Such monomer is sometimes hereinafter referred to as “monomer(a1-5)”. When the resin (A2) has the structural unit derived from themonomer (a1-5), a resist pattern tends to be obtained with less defects.

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆alkyl group that optionally has a halogen atom;

Z¹ represents a single bond or *—O—(CH₂)_(k4)—CO-L⁴-, k4 represents aninteger of 1 to 4, * represents a bond to L¹;

L¹, L², L³ and L⁴ independently represent *—O— or *—S—.

s1 represents an integer of 1 to 3;

s1′ represents an integer of 0 to 3.

In the formula (a1-5), R³¹ is preferably a hydrogen atom, a methyl groupor trifluoromethyl group;

L¹ is preferably —O—;

L² and L³ are independently preferably *—O— or *—S—, and more preferably—O— for one and —S— for another;

s1 is preferably 1;

s1′ is preferably an integer of 0 to 2;

Z¹ is preferably a single bond or —CH₂—CO—O—.

Examples of the monomer (a1-5) include monomers below.

When the resin (A2) contains the structural unit derived from themonomer (a 1-5), the proportion thereof is generally 1 to 50 mol %,preferably 3 to 45 mol %, and more preferably 5 to 40 mol %, withrespect to the total structural units (100 mol %) constituting the resin(A2).

<Acid Stable Monomer>

As the acid stable monomer, a monomer having a hydroxy group or alactone ring is preferable. When a resin containing the structural unitderived from a monomer having hydroxy group (hereinafter such acidstable monomer is sometimes referred to as “acid stable monomer (a2)”)or a acid stable monomer having a lactone ring (hereinafter such acidstable monomer is sometimes referred to as “acid stable monomer (a3)”)is used, the adhesiveness of resist pattern to a substrate andresolution of resist pattern tend to be improved.

<Acid Stable Monomer (a2)>

The acid stable monomer (a2), which has a hydroxy group, is preferablyselected depending on the kinds of an exposure light source at producingthe resist pattern.

When KrF excimer laser lithography (248 nm), or high-energy irradiationsuch as electron beam or EUV light is used for the resist composition,using the acid stable monomer having a phenolic hydroxy group such ashydroxystyrene as the acid stable monomer (a2) is preferable.

When ArF excimer laser lithography (193 nm), i.e., short wavelengthexcimer laser lithography is used, using the acid stable monomer havinga hydroxy adamantyl group represented by the formula (a2-1) as the acidstable monomer (a2) is preferable.

The acid stable monomer (a2) having the hydroxy group may be used as asingle monomer or as a combination of two or more monomers.

Examples of the acid stable monomer having hydroxy adamantyl include themonomer represented by the formula (a2-1).

wherein L^(a3) represents —O— or *—O—(CH₂)_(k2)—CO—O—;

k2 represents an integer of 1 to 7;

-   -   * represents a bind to —CO—;

R^(a14) represents a hydrogen atom or a methyl group;

R^(a15) and R^(a16) independently represent a hydrogen atom, a methylgroup or a hydroxy group;

o1 represents an integer of 0 to 10.

In the formula (a2-1), L^(a3) is preferably —O—, —O—(CH₂)_(f1)—CO—O—,here f1 represents an integer of 1 to 4, and more preferably —O—.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably an integer of 0 to 3, and more preferably an integer of0 or 1.

Examples of the acid stable monomer (a2-1) include monomers described inJP 2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a2-1-1) to the formula (a2-1-6), morepreferably monomers represented by the formula (a2-1-1) to the formula(a2-1-4), and still more preferably monomers represented by the formula(a2-1-1) and the formula (a2-1-3) below.

When the resin (A2) contains the acid stable structural unit derivedfrom the monomer represented by the formula (a2-1), the proportionthereof is generally 3 to 45 mol %, preferably 5 to 40 mol %, morepreferably 5 to 35 mol %, and still more preferably 5 to 30 mol %, withrespect to the total structural units (100 mol %) constituting the resin(A2).

<Acid Stable Monomer (a3)>

The lactone ring included in the acid stable monomer (a3) may be amonocyclic compound such as β-propiolactone ring, γ-butyrolactone,δ-valerolactone, or a condensed ring with monocyclic lactone ring andother ring. Among these, γ-butyrolactone and condensed ring withγ-butyrolactone and other ring are preferable.

Examples of the acid stable monomer (a3) having the lactone ring includemonomers represented by the formula (a3-1), the formula (a3-2) and theformula (a3-3). These monomers may be used as a single monomer or as acombination of two or more monomers.

wherein L^(a4) to L^(a6) independently represent —O— or*—O—(CH₂)_(k3)—CO—O—;

k3 represents an integer of 1 to 7, * represents a bind to —CO—;

R^(a18) to R^(a20) independently represent a hydrogen atom or a methylgroup;

R^(a21) in each occurrence represents a C₁ to C₄ alkyl group;

p1 represents an integer of 0 to 5;

R^(a22) to R^(a23) in each occurrence independently represent a carboxylgroup, cyano group, and a C₁ to C₄ alkyl group;

q1 and r1 independently represent an integer of 0 to 3.

In the formulae (a3-1) to (a3-3), L^(a4) to L^(a6) include the samegroup as described in L^(a3) above, and are independently preferably—O—, *—O—(CH₂)_(k3′)—CO—O—, here k3′ represents an integer of 1 to 4(preferably 1), and more preferably —O—;

R^(a18) to R^(a21) are independently preferably a methyl group.

R^(a22) and R^(a23) are independently preferably a carboxyl group, cyanogroup or methyl group;

p1 to r1 are independently preferably an integer of 0 to 2, and morepreferably an integer of 0 or 1.

Examples of the monomer (a3) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a3-1-1) to the formula (a3-1-4), the formula(a3-2-1) to the formula (a3-2-4), the formula (a3-3-1) to the formula(a3-3-4), more preferably monomers represented by the formula (a3-1-1)to the formula (a3-1-2), the formula (a3-2-3) to the formula (a3-2-4),and still more preferably monomers represented by the formula (a3-1-1)and the formula (a3-2-3) below.

When the resin (A2) contains the structural units derived from the acidstable monomer (a3) having the lactone ring, the total proportionthereof is preferably 5 to 70 mol %, more preferably 10 to 65 mol %,still more preferably 15 to 60 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A2).

When the resin (A2) is the copolymer of the acid labile monomer (a1) andthe acid stable monomer, the proportion of the structural unit derivedfrom the acid labile monomer (a1) is preferably 10 to 80 mol %, and morepreferably 20 to 60 mol %, with respect to the total structural units(100 mol %) constituting the resin (A2).

The proportion of the structural unit derived from the monomer having anadamantyl group (in particular, the monomer having the acid labile group(a1-1)) is preferably 15 mol % or more with respect to the structuralunits derived from the acid labile monomer (a1). As the mole ratio ofthe structural unit derived from the monomer having an adamantyl groupincreases within this range, the dry etching resistance of the resultingresist improves.

The resin (A2) preferably is a copolymer of the acid labile monomer (a1)and the acid stable monomer. In this copolymer, the acid labile monomer(a1) is preferably at least one of the acid labile monomer (a1-1) havingan adamantyl group and the acid labile monomer (a1-2) having acyclohexyl group, and more preferably is the acid labile monomer (a1-1).

The acid stable monomer is preferably the acid stable monomer (a2)having a hydroxy group and/or the acid stable monomer (a3) having alactone ring. The acid stable monomer (a2) is preferably the monomerhaving the hydroxyadamantyl group (a2-1).

The acid stable monomer (a3) is preferably at least one of the monomerhaving the γ-butyrolactone ring (a3-1) and the monomer having thecondensed ring of the γ-butyrolactone ring and the norbornene ring(a3-2).

The resin (A2) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of the acidlabile monomer (a1) and/or at least one of the acid stable monomer (a2)having a hydroxy group and/or at least one of the acid stable monomer(a3) having a lactone ring and/or at least one of a known compound.

The weight average molecular weight of the resin (A2) is preferably2,500 or more (more preferably 3,000 or more, and still more preferably4,000 or more), and 50,000 or less (more preferably 30,000 or less, andstill more preferably 10,000 or less).

In the present resist composition, the weight ratio of the resins(A1)/(A2) (weight ratio) is preferably, for example, 0.01/10 to 5/10,more preferably 0.05/10 to 3/10, still more preferably 0.1/10 to 2/10,in particular, preferably 0.2/10 to 1/10.

<Resin Other than Resin (A1) and Resin (A2)>

The resist composition of the present invention may include a resinother than the resin (A1) and the resin (A2) described above. Such resinis a resin having at least one of the structural unit derived from theacid labile monomer (a1), at least one of the structural unit derivedfrom the acid stable monomer, as described above, and/or at least one ofthe structural unit derived from a known monomer in this field.

The proportion of the resin (A) can be adjusted with respect to thetotal solid proportion of the resist composition. For example, theresist composition of the present invention preferably contains 80weight % or more and 99 weight % or less of the resin (A), with respectto the total solid proportion of the resist composition.

In the specification, the term “solid proportion of the resistcomposition” means the entire proportion of all ingredients other thanthe solvent (E). For example, if the proportion of the solvent (E) is 90weight %, the solid proportion of the resist composition is 10 weight %.

The proportion of the resin (A) and the solid proportion of the resistcomposition can be measured with a known analytical method such as, forexample, liquid chromatography and gas chromatography.

<Acid Generator (II)>

The acid generator included in the resist composition of the presentinvention is represented by the formula (II);

wherein R^(b1) and R^(b2) independently represent a fluorine atom or aC₁ to C₆ perfluoroalkyl group;

L^(b1) represents a C₁ to C₁₇ divalent saturated hydrocarbon group, oneor more —CH₂— contained in the saturated hydrocarbon group may bereplaced by —O— or —CO—;

ring W^(b1) represents a C₂ to C₃₆ heterocycle;

R^(b3) represents a hydrogen atom or a C₁ to C₁₂ hydrocarbon group, oneor more —CH₂— contained in the hydrocarbon group may be replaced by —O—or —CO—;

R^(b4) in each occurrence independently represent a C₁ to C₆ hydrocarbongroup, one or more —CH₂— contained in the hydrocarbon group may bereplaced by —O— or —CO—;

m represents an integer of 0 to 6; and

Z¹⁺ represents an organic cation.

In the formula (II), a moiety having a negative charge in which anorganic cation, Z¹⁺, having a positive charge is removed sometimesrefers to as a sulfonate anion.

Examples of the perfluoroalkyl group of R^(b1) and R^(b2) includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl and perfluorohexyl groups.

The divalent saturated hydrocarbon group of L^(b1) may be a linear chainalkanediyl group, a branched chain alkanediyl group, a mono- orpolycyclic divalent saturated alicyclic hydrocarbon group and combinedtwo or more thereof.

Specific examples of the linear chain alkanediyl group includemethylene, ethylene, propane-1,3-diyl, propane-1,2-diyl,butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl,octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl,dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl,pentadecane-1,15-diyl, hexadecane-1,16-diyl, heptadecane-1,17-diyl,ethane-1,1-diyl, propan-1,1-diyl and propan-2,2-diyl groups.

Specific examples of the branched chain alkanediyl group include a groupin which a linear chain alkanediyl group has a side chain of an alkylgroup (especially a C₁ to C₄ alkyl group such as methyl, ethyl, propyl,isopropyl, butyl, sec-butyl, tert-butyl groups) such as butane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, pentane-1,4-diyl and2-methylbutane-1,4-diyl groups.

Specific examples of the monocyclic saturated alicyclic hydrocarbongroup include cycloalkanediyl group, such as cyclobutan-1,3-diyl,cyclopenthan-1,3-diyl, cyclohexan-1,2-diyl, 1-methylcyclohexan-1,2-diyl,cyclohexan-1,4-diyl, cyclooctan-1,2-diyl and cyclooctan-1,5-diyl groups.

Specific examples of the polycyclic saturated alicyclic hydrocarbongroup include norbornane-2,3-diyl, norbornane-1,4-diyl,norbornane-2,5-diyl, adamantane-1,5-diyl and adamantane-2,6-diyl groups.

Examples of the divalent saturated alicyclic hydrocarbon group may alsoinclude the group in which any one of hydrogen atom on a monovalentsaturated cyclic hydrocarbon group described below is removed.

Examples of L^(b1) in which one or more —CH₂— contained in the divalentsaturated hydrocarbon group is replaced by —O— or —CO— include, forexample, groups represented by the formula (L1-1) to the formula (L1-6).In the formula (L1-1) to the formula (L1-6), the group is represented soas to correspond with two sides of the formula (II), that is, the leftside of the group bonds to the carbon atom of C(R^(b1))(R^(b2))— and theright side of the group bonds to ring W^(b1). Examples of the formula(L1-1) to the formula (L1-6) are the same as above.

wherein L^(b2) represents a single bond or a C₁ to C₁₅ divalentsaturated hydrocarbon group;

L^(b3) represents a single bond or a C₁ to C₁₂ divalent saturatedhydrocarbon group;

L^(b4) represents a C₁ to C₁₃ divalent saturated hydrocarbon group;

L^(b5) represents a C₁ to C₁₅ divalent saturated hydrocarbon group;

L^(b6) and L^(b7) independently represent a C₁ to C₁₅ divalent saturatedhydrocarbon group;

L^(b8) represents a C₁ to C₁₄ divalent saturated hydrocarbon group;

L^(b9) represents a C₁ to C₁₄ divalent saturated hydrocarbon group;

L^(b10) represents a C₁ to C₁₁ divalent saturated hydrocarbon group.

Specific examples of the divalent group represented by the formula(L1-1) include groups below. In the formula below, * represent a bond.

Specific examples of the divalent group represented by the formula(L1-2) include groups below.

Specific examples of the divalent group represented by the formula(L1-3) include groups below.

Specific examples of the divalent group represented by the formula(L1-4) include a group below.

Specific examples of the divalent group represented by the formula(L1-5) include groups below.

Specific examples of the divalent group represented by the formula(L1-6) include groups below.

The heterocycle of ring W^(b1) may be a ring having one or more nitrogenatoms, and it may further have one or more nitrogen atom, one or moreoxygen atom, or one or more sulfur atom. The heterocycle may has any ofaromaticity or non-aromaticity, and any of a monocyclic or a polycycliccompound, or condensed or bridged ring.

Specific examples of the heterocycle include a ring below. One or more—CH₂— contained in the heterocycle may be replaced by —O— or —CO—. Amongthese, a ring represented by the formula (W1), a ring represented by theformula (W2) and a ring represented by the formula (W3) arepreferable. * represents a bond to L^(b1).

The hydrocarbon group of R^(b3) and R^(b4) includes an aliphatichydrocarbon group, an alicyclic hydrocarbon group and an aromatichydrocarbon group.

Examples of the aliphatic hydrocarbon group include an alkyl group suchas methyl, ethyl, n-propyl, 1-methylethyl (isopropyl), n-butyl,1,1-dimethylethyl (tert-butyl), 2,2-dimethylethyl, 1-methylpropyl,2-methylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl,n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, n-hexyl,1-propylbutyl, pentyl, 1-methylpentyl, 1,4-dimethylhexyl, heptyl,1-methylheptyl, octyl, methyloctyl, methylnonyl, 2-ethylhexhyl, nonyl,decyl, undecyl and dodecyl groups.

The alicyclic hydrocarbon group may be any of a mono- or poly-cyclichydrocarbon group. Examples of the monocyclic hydrocarbon groups includea cycloalkyl group such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl. Examples of the polycyclichydrocarbon groups include a group which is obtained by hydrogenating acondensed aromatic hydrocarbon group such as hydronaphtyl, and a bridgedcyclic hydrocarbon group such as adamantyl, norbornyl andmethylnorbornyl groups. Examples of the alicyclic hydrocarbon groupfurther include a group in which a bridged ring (e.g. norbornane ring)is condensed with a monocycle (e.g. cycloheptane ring, cyclohexane ring)or a polycycle (e.g. decahydronaphthalene ring), a group in which two ormore bridged rings are condensed, and a combination thereof (e.g.methylcyclohexyl, dimethylcyclohexyl and methyl norbornyl groups) asfollows.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, p-methylphenyl, p-ethylphenyl, p-tert-butylphenyl,p-cyclohexylphenyl, p-methoxyphenyl, p-adamantylphenyl, tolyl, xylyl,cumenyl, mesityl, biphenyl, anthryl, phenanthryl, 2,6-diethylphenyl and2-methyl-6-ethylphenyl groups.

In the acid generator (II), R^(b1) and R^(b2) independently arepreferably a trifluoromethyl or a fluorine atom, and more preferably afluorine atom.

For L^(b1), any of the groups represented by the formula (L1-1) to theformula (L1-4) are preferable, any of the groups represented by theformula (L1-1) or the formula (L1-2) is more preferable, the grouprepresented by the formula (L1-1) is still more preferable, among these,the divalent group represented by the formula (L1-1) in which L^(b2)represents a single bond or a C₁ to C₆ saturated hydrocarbon group,i.e., *—CO—O—(CH₂)_(t)— wherein t represents an integer of 0 to 6, *represents a bond to —C(R^(b1))(R^(b2))— is preferable and, the divalentgroup represented by the formula (L1-1) in which L^(b2) represents asingle bond or a methylene group is more preferable, and the divalentgroup represented by the formula (L1-1) in which L^(b2) represents asingle, i.e., *—CO—O—, is still more preferable.

For R^(b3), a hydrogen atom, a methyl group, an ethyl group and atert-butoxycarbonyl group are preferable, and a hydrogen atom, a methylgroup and a tert-butoxycarbonyl group are more preferable.

m is preferably 0, but when m represents an integer of 0 to 6, R^(b4) ispreferably methyl, ethyl, methylcarbonyloxy (acetyloxy), and ethylcarbonyloxy groups.

Examples of the acid generator (II) include compounds below.

Examples of the cation Z¹⁺ include an organic onium cation such as anorganic sulfonium cation, an organic iodonium cation, an organicammonium cation, a benzothiazolium cation and an organic phosphoniumcation. Among these, an organic sulfonium cation and an organic iodoniumcation are preferable, and an aryl sulfonium cation is more preferable.

Specific examples of Z¹⁺ include a cation represented by any of theformula (Z1) to the formula (Z4).

wherein P^(a), P^(b) and P^(c) independently represent a C₁ to C₃₀aliphatic hydrocarbon group, a C₃ to C₃₆ alicyclic hydrocarbon group ora C₆ to C₃₆ aromatic hydrocarbon group, or Pa and Pb may be bonded toform at least one sulfur atom-containing ring, one or more hydrogen atomcontained in the aliphatic hydrocarbon group may be replaced with ahydroxy group, a C₃ to C₁₈ alicyclic hydrocarbon group, a C₁ to C₁₂alkoxy group or a C₆ to C₁₈ aromatic hydrocarbon group, one or morehydrogen atom contained in the alicyclic hydrocarbon group may bereplaced with a halogen atom, C₁ to C₁₈ alkyl group, a C₂ to C₄ acylgroup or a glycidyloxy group, one or more hydrogen atom contained in thearomatic hydrocarbon group may be replaced with a halogen atom, ahydroxy group or a C₁ to C₁₂ alkoxy group;

P⁴ and P⁵ in each occurrence independently represent a hydroxy group, aC₁ to C₁₂ aliphatic hydrocarbon or a C₁ to C₁₂ alkoxy group;

P⁶ and P⁷ independently represent a C₁ to C₃₆ aliphatic hydrocarbon or aC₃ to C₃₆ alicyclic hydrocarbon group, or P⁶ and P⁷ may be bondedtogether to form a three- to twelve-membered ring (preferably a three-to seven-membered ring) with a sulfur atom which is bonded thereto, andone or more —CH₂— contained in the ring may be replaced by —O—, —S— or—CO—;

P⁸ represents a hydrogen atom, a C₁ to C₃₆ aliphatic hydrocarbon group,a C₃ to C₃₆ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatichydrocarbon group;

P⁹ represents a C₁ to C₁₂ aliphatic hydrocarbon group, a C₃ to C₁₈alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group,one or more hydrogen atoms contained in the aliphatic hydrocarbon groupmay be replaced by a C₆ to C₁₈ aromatic hydrocarbon group, one or morehydrogen atom contained in the aromatic hydrocarbon group may bereplaced with a C₁ to C₁₂ alkoxy group or an alkyl carbonyloxy group;

P⁸ and P⁹ may be bonded together to form a three- to twelve-memberedring (preferably a three- to seven-membered ring) with —CH—CO— which isbonded thereto, and one or more —CH₂— contained in the ring may bereplaced by —O—, —S— or —CO—;

P¹⁰ to P¹⁵ in each occurrence independently represent a hydroxy group, aC₁ to C₁₂ aliphatic hydrocarbon or a C₁ to C₁₂ alkoxy group;

E represents —S— or —O—;

i, j, p, r, x and y independently represent an integer of 0 to 5;

q represents an integer of 0 or 1;

v and w independently represent an integer of 0 to 4.

Examples of the aliphatic hydrocarbon group include an alkyl group suchas methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, octyl and 2-ethylhexyl groups. The aliphatic hydrocarbongroup of P⁶ to P⁸ is preferably a group having 1 to 12 carbon atoms.

Examples of the aliphatic hydrocarbon group in which one or morehydrogen atoms are replaced by an alicyclic hydrocarbon group1-(1-adamatane-1-yl)-alkane-1-yl.

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon groups such as, cycloalkyl group, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl; apolycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl andnorbornyl (i.e., bicyclo[2.2.1]heptyl) groups as well as groups below.

In particular, the alicyclic hydrocarbon group of P⁶ to P⁸ is preferablya C₃ to C₁₈ alicyclic hydrocarbon group, and more preferably a C₄ to C₁₂alicyclic hydrocarbon group.

Examples of the alicyclic hydrocarbon group in which one or morehydrogen atoms are replaced by an alkyl group include methyl cyclohexyl,dimethyl cyclohexyl, 2-alkyladamantane-2-yl, methyl norbornyl andisobornyl groups.

Examples of the aromatic hydrocarbon group include phenyl, naphthyl,anthryl, p-methylphenyl, p-ethylphenyl, p-tert-butylphenyl,p-cyclohexylphenyl, p-methoxyphenyl, p-adamantylphenyl, tolyl, xylyl,cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and2-methyl-6-ethylphenyl groups.

When the aromatic hydrocarbon include an aliphatic hydrocarbon group oran alicyclic hydrocarbon group, a C₁ to C₃₆ aliphatic hydrocarbon groupor a C₃ to C₃₆ alicyclic hydrocarbon group is preferable.

Examples of the alkyl group in which one or more hydrogen atoms arereplaced by an aromatic hydrocarbon group, i.e., aralkyl group includebenzyl, phenethyl phenylpropyl, trityl, naphthylmethyl and naphthylethylgroups.

Examples of the alkoxyl group include methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, n-hexyloxy,heptyloxy, octyloxy, 2-ethylhexoxy, nonyloxy, decyloxy, undecyloxy anddodecyloxy groups.

Examples of the halogen atom include fluorine, chlorine, bromine andiodine atoms.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the alkylcarbonyloxy group include methylcarbonyloxy,ethylcarbonyloxy, n-propylcarbonyloxy, isopropylcarbonyloxy,n-butylcarbonyloxy, sec-butylcarbonyloxy, tert-butylcarbonyloxy,pentylcarbonyloxy, hexylcarbonyloxy, octylcarbonyloxy and2-ethylhexylcarbonyloxy groups.

The sulfur-containing ring formed by P^(a) and P^(b) may be either ofmonocyclic or polycyclic, aromatic or non-aromatic, or saturated orunsaturated ring, and may further have at least one of sulfur atomand/or at least one of oxygen atom as long as the ring has one sulfuratom. The ring is preferably a ring having 3 to 18 carbon atoms, andmore preferably a ring having 4 to 12 carbon atoms.

Examples of the ring formed by P⁶ and P⁷ bonded together with a sulfuratom includes, for example, thiolane-1-ium ring (tetrahydrothiopheniumring), thian-1-ium ring and 1,4-oxathian-4-ium ring.

Examples of the ring formed by P⁸ and P⁹ bonded together with —CH—CO—include oxocycloheptane ring, oxocyclohexane ring, oxonorbornane ringand oxoadamantane ring.

Among the cations represented by the formula (Z1) to the formula (Z4),the cation represented by the formula (Z1) is preferable, the cationrepresented by the formula (Z5) is more preferable, and triphenylsulfonium cation (z1=z2=z3=0 in the formula (Z5)), diphenyl sulfoniumcation (z1=z2=0, z3=1, and R³ is a methyl group in the formula (Z5)),and tritolyl sulfonium cation (z1=z2=z3=1, P¹, P² and P³ are a methylgroup in the formula (Z5)) are more preferable.

wherein P′ to P³ in each occurrence independently represent a halogenatom, a hydroxy group, a C₁ to C₃₆ aliphatic hydrocarbon group, a C₃ toC₃₆ alicyclic hydrocarbon group or a C₁ to C₁₂ alkoxy group, or two ofP¹ to P³ may be bonded together to form a ring which contains a sulfuratom;

z1, z2 and z3 independently represent an integer of 0 or 5.

The sulfur-containing ring formed by two of P¹ to P³ may be either ofmonocyclic or polycyclic, aromatic or non-aromatic, or saturated orunsaturated ring, and may further have at least one of sulfur atomand/or at least one of oxygen atom as long as the ring has one sulfuratom.

The aliphatic hydrocarbon group preferably has 1 to 12 carbon atoms, andthe alicyclic hydrocarbon group preferably has 4 to 36 carbon atoms.

Among these, P¹ to P³ are in each occurrence independently preferably ahalogen atom (more preferably fluorine atom), a hydroxy group, a C₁ toC₁₂ alkyl group or a C₁ to C₁₂ alkoxy group, or two of P¹ to P³ arepreferably bonded together to form a ring which contains a sulfur atomand an oxygen atom.

z1, z2 and z3 are independently preferably 0 or 1.

Specific examples of the cation of the formula (Z1) or the formula (Z5)include a cation below.

Specific examples of the cation of the formula (Z5) which formed by asulfur atom-containing ring include a cation below.

Specific examples of the cation of the formula (Z1) include a cationbelow.

Specific examples of the cation of the formula (Z2) include a cationbelow.

Specific examples of the cation of the formula (Z3) include a cationbelow.

Specific examples of the cation of the formula (Z4) include a cationbelow.

The acid generator (II) is a compound combined the above anion with anorganic cation. The above anion and the organic cation may optionally becombined, but the salts shown below are preferable. In the formulabelow, the definition of the substituents represent the same meaning asdescribed above.

Further, the salts below are more preferable.

The acid generator (II) can be produced by a known method in the field.

For example, a salt represented by the formula (IIa) in which L^(b1) ofthe acid generator (II) is —CO—O— can be obtained by reacting a saltrepresented by the formula (IIa-1) with a compound represented by theformula (IIa-2) in a solvent.

wherein R^(b1) to R^(b3), Z¹⁺ and ring W^(b1) represent the same meaningas described above.

Examples of the solvent include chloroform.

Example of the compound represented by the formula (IIa-2) include4-hydroxy-1-methylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidineand tropine.

The compound represented by the formula (IIa-1) can be obtained byreacting a salt represented by the formula (IIa-4) with a compoundrepresented by the formula (IIa-3).

The compound represented by the formula (IIa-3) can be synthesizedaccording to the method described in JP-2008-13551A.

wherein R^(b1) to R^(b2) and Z¹⁺ represent the same meaning as describedabove.

In the resist composition of the present invention, the acid generator(II) may be used as a single compound or as a combination of two or morecompounds.

<Other Acid Generator>

The resist composition of the present invention contains at least onekinds of acid generator (II) and may further include a known acidgenerator other than the acid generator (II) (hereinafter is sometimesreferred to as “acid generator (B)”).

The acid generator (B) may be any of a non-ionic-based and anionic-based acid generator, and ionic-based acid generator ispreferable. Examples of the acid generator (B) include, an acidgenerator having a cation and an anion which are different from these ofthe acid generator (II), an acid generator having a cation which is thesame as these of the acid generator (II) and an anion of a known anionwhich is different from that of the acid generator (II), and an acidgenerator having an anion which is the same as these of the acidgenerator (II) and a cation of a known anion which is different fromthat of the acid generator (II).

Preferred acid generators (B) are represented by the formula (B1-1) tothe formula (B1-20). Among these, the formulae (B1-1), (B1-2), (B1-6),(B1-11), (B1-12), (B1-13) and (B1-14) which contain triphenyl sulfoniumcation, and the formulae (B1-3) and (B1-7) which contain tritolylsulfonium cation are preferable.

In the resist composition of the present invention, the acid generator(B) may be used as a single compound or as a combination of two or morecompounds.

In the resist composition of the present invention, the proportion ofthe acid generator (II) is preferably not less than 1 weight % (and morepreferably not less than 3 weight %), and not more than 30 weight % (andmore preferably not more than 25 weight %), with respect to the resin(A).

When the resist composition of the present invention contains the acidgenerator (II) and the acid generator (B), the total proportion of theacid generator (II) and the acid generator (B) is preferably not lessthan 1 weight % (and more preferably not less than 3 weight %), and notmore than 40 weight % (and more preferably not more than 35 weight %,with respect to the resin (A). In this case, the weight ratio of theacid generator (II) and the acid generator (B) is preferably, forexample, 5:95 to 95:5, more preferably 10:90 to 90:10 and still morepreferably 15:85 to 85:15.

<Solvent (E)>

The resist composition of the present invention preferably includes asolvent (E). The proportion of the solvent (E) 90 weight % or more,preferably 92 weight % or more, and more preferably 94 weight % or more,and also preferably 99.9 weight % or less and more preferably 99 weight% or less. The proportion of the solvent (E) can be measured with aknown analytical method such as, for example, liquid chromatography andgas chromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; ethers such as diethylene glycol dimethyl ether;esters such as ethyl lactate, butyl acetate, amyl acetate and ethylpyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanoneand cyclohexanone; and cyclic esters such as γ-butyrolactone. Thesesolvents may be used as a single solvent or as a mixture of two or moresolvents.

<Basic Compound (C)>

The resist composition of the present invention may contain a basiccompound (C). The basic compound (C) is a compound having a property toquench an acid, in particular, generated from the acid generator (B),and called “quencher”.

As the basic compounds (C), nitrogen-containing basic compounds (forexample, amine and basic ammonium salt) are preferable. The amine may bean aliphatic amine or an aromatic amine. The aliphatic amine includesany of a primary amine, secondary amine and tertiary amine. The aromaticamine includes an amine in which an amino group is bonded to an aromaticring such as aniline, and a hetero-aromatic amine such as pyridine.

Preferred basic compounds (C) include compounds presented by the formula(C1) to the formula (C8) and the formula (C1-1) as described below.Among these, the basic compound presented by the formula (C1-1) is morepreferable.

wherein R^(c1), R^(c2) and R^(c3) independently represent a hydrogenatom, a C₁ to C₆ alkyl group, C₅ to C₁₀ alicyclic hydrocarbon group or aC₆ to C₁₀ aromatic hydrocarbon group, one or more hydrogen atomcontained in the alkyl group and alicyclic hydrocarbon group may bereplaced by a hydroxy group, an amino group or a C₁ to C₆ alkoxyl group,one or more hydrogen atom contained in the aromatic hydrocarbon groupmay be replaced by a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, aC₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatichydrocarbon group.

wherein R^(c2) and R^(c3) have the same definition of the above;

R^(c4) in each occurrence represents a C₁ to C₆ alkyl group, a C₁ to C₆alkoxyl group, a C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀aromatic hydrocarbon group;

m3 represents an integer 0 to 3.

wherein R^(c5), R^(c6), R^(c7) and R^(c8) independently represent theany of the group as described in R^(c1) of the above;

R^(c9) in each occurrence independently represents a C₁ to C₆ alkylgroup, a C₃ to C₆ alicyclic hydrocarbon group or a C₂ to C₆ alkanoylgroup;

n3 represents an integer of 0 to 8.

wherein R^(c10), R^(c11), R^(c12), R^(c13) and R^(c16) independentlyrepresent the any of the groups as described in R^(c1);

R^(c14), R^(c15) and R^(c17) in each occurrence independently representthe any of the groups as described in R^(c4);

o3 and p3 represent an integer of 0 to 3;

L^(c1) represents a divalent C₁ to C₆ alkanediyl group, —CO—, —C(═NH)—,—S— or a combination thereof.

wherein R^(c18), R^(c19) and R^(c20) in each occurrence independentlyrepresent the any of the groups as described in R^(c4);

q3, r3 and s3 represent an integer of 0 to 3;

L^(c2) represents a single bond, a C₁ to C₆ alkanediyl group, —CO—,—C(═NH)—, —S— or a combination thereof.

In the formula (C1) to the formula (C8) and the formula (C1-1), thealkyl, alicyclic hydrocarbon, aromatic, alkoxy and alkanediyl groupsinclude the same examples as the above.

Examples of the alkanoyl group include acetyl, 2-methyl acetyl,2,2-dimethyl acetyl, propionyl, butyryl, isobutyryl, pentanoyl and2,2-dimethyl propionyl groups.

Specific examples of the amine represented by the formula (C1) include1-naphtylamine, 2-naphtylamine, aniline, diisopropylaniline, 2-, 3- or4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline,diphenylamine, hexylamine, heptylamine, octylamine, nonylamine,decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylene diamine, tetramethylene diamine,hexamethylene diamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane and4,4′-diamino-3,3′-diethyldiphenylmethane.

Among these, diisopropylaniline is preferable, particularly2,6-diisopropylaniline is more preferable as the basic compounds (C)contained in the present resist composition.

Specific examples of the compound represented by the formula (C2)include, for example, piperazine.

Specific examples of the compound represented by the formula (C3)include, for example, morpholine.

Specific examples of the compound represented by the formula (C4)include, for example, piperidine, a hindered amine compound havingpiperidine skeleton described in JP H11-52575-A.

Specific examples of the compound represented by the formula (C5)include, for example, 2,2′-methylenebisaniline.

Specific examples of the compound represented by the formula (C6)include, for example, imidazole and 4-methylimidazole.

Specific examples of the compound represented by the formula (C7)include, for example, pyridine and 4-methylpyridine.

Specific examples of the compound represented by the formula (C8)include, for example, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide,2,2′-dipyridylamine, 2,2′-dipicolylamine and bipyridine.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethyl ammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butyl ammonium salicylate andcholine.

The proportion of the basic compound (C) is preferably 0.01 to 5 weight%, more preferably 0.01 to 3 weight %, and still more preferably 0.01 to1 weight % with respect to the total solid proportion of the resistcomposition.

<Other Ingredient (Hereinafter is Sometimes Referred to as “OtherIngredient (F)”>

The resist composition can also include small amounts of various knownadditives such as sensitizers, dissolution inhibitors, surfactants,stabilizers, and dyes, as needed.

<Preparing the Resist Composition>

The present resist composition can be prepared by mixing the resin (A1),the resin (A2) and the acid generator (II), and the basic compound (C),the solvent (E), the acid generator (B) and the other ingredient (F) asneeded. There is no particular limitation on the order of mixing. Themixing may be performed in an arbitrary order. The temperature of mixingmay be adjusted to an appropriate temperature within the range of 10 to40° C., depending on the kinds of the resin and solubility in thesolvent (E) of the resin. The time of mixing may be adjusted to anappropriate time within the range of 0.5 to 24 hours, depending on themixing temperature. There is no particular limitation to the tool formixing. An agitation mixing may be adopted.

After mixing the above ingredients, the present resist compositions canbe prepared by filtering the mixture through a filter having about 0.003to 0.2 μm pore diameter.

<Method for Producing a Resist Pattern>

The method for producing a resist pattern of the present inventionincludes the steps of:

(1) applying the resist composition of the present invention onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

Applying the resist composition onto the substrate can generally becarried out through the use of a resist application device, such as aspin coater known in the field of semiconductor microfabricationtechnique.

Drying the applied composition layer, for example, can be carried outusing a heating device such as a hotplate (so-called “prebake”), adecompression device, or a combination thereof. Thus, the solventevaporates from the resist composition and a composition layer with thesolvent removed is formed. The condition of the heating device or thedecompression device can be adjusted depending on the kinds of thesolvent used. The temperature in this case is generally within the rangeof 50 to 200° C. Moreover, the pressure is generally within the range of1 to 1.0×10⁵ Pa.

The composition layer thus obtained is generally exposed using anexposure apparatus or a liquid immersion exposure apparatus. Theexposure is generally carried out through a mask that corresponds to thedesired pattern. Various types of exposure light source can be used,such as irradiation with ultraviolet lasers such as KrF excimer laser(wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂ excimerlaser (wavelength: 157 nm), or irradiation with far-ultravioletwavelength-converted laser light from a solid-state laser source (YAG orsemiconductor laser or the like), or vacuum ultraviolet harmonic laserlight or the like. Also, the exposure device may be one which irradiateselectron beam or extreme-ultraviolet light (EUV).

After exposure, the composition layer is subjected to a heat treatment(so-called “post-exposure bake”) to promote the deprotection reaction.The heat treatment can be carried out using a heating device such as ahotplate. The heating temperature is generally in the range of 50 to200° C., preferably in the range of 70 to 150° C.

The composition layer is developed after the heat treatment, generallywith an alkaline developing solution and using a developing apparatus.The development here means to bring the composition layer after the heattreatment into contact with an alkaline solution. Thus, the exposedportion of the composition layer is dissolved by the alkaline solutionand removed, and the unexposed portion of the composition layer remainson the substrate, whereby producing a resist pattern. Here, as thealkaline developing solution, various types of aqueous alkalinesolutions used in this field can be used. Examples include aqueoussolutions of tetramethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (common name: choline).

After the development, it is preferable to rinse the substrate and thepattern with ultrapure water and to remove any residual water thereon.

<Application>

The resist composition of the present invention is useful as the resistcomposition for excimer laser lithography such as with ArF, KrF or thelike, and the resist composition for electron beam (EB) exposurelithography and extreme-ultraviolet (EUV) exposure lithography, as wellas liquid immersion exposure lithography.

The resist composition of the present invention can be used insemiconductor microfabrication and in manufacture of liquid crystals,thermal print heads for circuit boards and the like, and furthermore inother photofabrication processes, which can be suitably used in a widerange of applications.

EXAMPLES

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention.

All percentages and parts expressing the content or amounts used in theExamples and Comparative Examples are based on weight, unless otherwisespecified.

The structure of a compound is measured by MASS (LC: manufactured byAgilent, 1100 type, MASS: manufactured by Agilent, LC/MSD type or LC/MSDTOF type).

The weight average molecular weight is a value determined by gelpermeation chromatography.

Apparatus: HLC-8120GPCtype (Tosoh Co. Ltd.)

Column: TSK gel Multipore HXL-M x 3+guardcolumn (Tosoh Co. Ltd.)

Eluant: tetrahydrofuran

Flow rate: 1.0 mL/min

Detecting device: RI detector

Column temperature: 40° C.

Injection amount: 100 μL

Standard material for calculating molecular weight: standard polystylene(Toso Co. ltd.)

Synthesis Example 1 Synthesis of Compound Represented by the Formula (A)

10.00 parts of a compound (A-2), 40.00 parts of tetrahydrofuran and 7.29parts of pyridine were mixed, and stirred for 30 minutes at 23° C. Theobtained mixture was cooled to 0° C. To this mixture, 33.08 parts of acompound (A-1) was added over 1 hour while maintaining at the sametemperature. The temperature of the mixture was then elevated to about23° C., and the mixture was stirred for 3 hour at the same temperature.361.51 parts of ethyl acetate and 20.19 parts of 5% of hydrochloric acidsolution were added to the obtained mixture, the mixture was stirred for30 minutes at 23° C. The obtained solution was allowed to stand, andthen separated to recover an organic layer. To the recovered organiclayer, 81.42 parts of a saturated sodium hydrogen carbonate was added,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to recover the organic layer. To therecovered organic layer was added 90.38 parts of ion-exchanged water,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to wash the organic layer with water. Thesewashing operations were repeated for 5 times. The obtained organic layerwas concentrated, resulting in 23.40 parts of the compound (A).

MS (mass spectroscopy): 326.0 (molecular ion peak)

Synthesis Example 2 Synthesis of Compound Represented by the Formula (B)

88.00 parts of a compound (B-2), 616.00 parts of methyl isobutyl ketoneand 60.98 parts of pyridine were mixed, and stirred for 30 minutes at23° C. The obtained mixture was cooled to 0° C. To this mixture, 199.17parts of a compound (B-1) was added over 1 hour while maintaining at thesame temperature. The temperature of the mixture was then elevated toabout 10° C., and the mixture was stirred for 1 hour at the sametemperature. 1446.22 parts of n-heptane and 703.41 parts of 2% ofhydrochloric acid solution were added to the obtained mixture, themixture was stirred for 30 minutes at 23° C. The obtained solution wasallowed to stand, and then separated to recover an organic layer. To therecovered organic layer, 337.64 parts of 2% of hydrochloric acidsolution was added to obtain a mixture, and the mixture was stirred for30 minutes at 23° C. The obtained solution was allowed to stand, andthen separated to recover an organic layer. To the recovered organiclayer, 361.56 parts of ion-exchanged water was added, and the obtainedsolution was stirred for 30 minutes at 23° C., allowed to stand, andthen separated to wash the organic layer with water. To the obtainedorganic layer, 443.92 parts of 10% of potassium carbonate was added, andthe obtained solution was stirred for 30 minutes at 23° C., allowed tostand, and then separated to recover the organic layer. These washingoperations were repeated for 2 times. To the obtained organic layer,361.56 parts of ion-exchanged water was added, and the obtained solutionwas stirred for 30 minutes at 23° C., allowed to stand, and thenseparated to wash the organic layer with water. These washing operationswere repeated for 5 times. The obtained organic layer was concentrated,resulting in 163.65 parts of the compound (B).

MS (mass spectroscopy): 276.0 (molecular ion peak)

Synthesis Example 3 Synthesis of Compound Represented by the Formula (E)

30.00 parts of a compound (E-2), 210.00 parts of methyl isobutyl ketoneand 18.00 parts of pyridine were mixed, and stirred for 30 minutes at23° C. The obtained mixture was cooled to 0° C. To this mixture, 48.50parts of a compound (E-1) was added over 1 hour while maintaining at thesame temperature. The temperature of the mixture was then elevated toabout 5° C., and the mixture was stirred for 1 hour at the sametemperature. Thus obtained reactant was added to 630 parts of ethylacetate, 99.68 parts of 5% of hydrochloric acid solution and 126 partsof ion-exchanged water to obtain a mixture, the mixture was stirred for30 minutes at 23° C. The obtained solution was allowed to stand, andthen separated to recover an organic layer. To the recovered organiclayer, 86.50 parts of 10% of potassium carbonate solution was added toobtain a mixture, and the mixture was stirred for 30 minutes at 23° C.The obtained solution was allowed to stand, and then separated torecover an organic layer. These washing operations were repeated for twotimes. To the recovered organic layer, 157.50 parts of ion-exchangedwater was added, and the obtained solution was stirred for 30 minutes at23° C., allowed to stand, and then separated to wash the organic layerwith water. These washing operations were repeated for five times. Theobtained organic layer was concentrated, resulting in 27.61 parts of thecompound (E).

MS (mass spectroscopy): 354.1 (molecular ion peak)

Synthesis Example 4 Synthesis of Compound Represented by the Formula (F)

27.34 parts of a compound (F-2), 190.00 parts of methyl isobutyl ketoneand 18.00 parts of pyridine were mixed, and stirred for 30 minutes at23° C. The obtained mixture was cooled to 0° C. To this mixture, 48.50parts of a compound (F-1) was added over 1 hour while maintaining at thesame temperature. The temperature of the mixture was then elevated toabout 5° C., and the mixture was stirred for 1 hour at the sametemperature. Thus obtained reactant was added to 570 parts of ethylacetate, 99.68 parts of 5% of hydrochloric acid solution and 126 partsof ion-exchanged water to obtain a mixture, the mixture was stirred for30 minutes at 23° C. The obtained solution was allowed to stand, andthen separated to recover an organic layer. To the recovered organiclayer, 86.50 parts of 10% of potassium carbonate solution was added toobtain a mixture, and the mixture was stirred for 30 minutes at 23° C.The obtained solution was allowed to stand, and then separated torecover an organic layer. These washing operations were repeated for twotimes. To the recovered organic layer, 150 parts of ion-exchanged waterwas added, and the obtained solution was stirred for 30 minutes at 23°C., allowed to stand, and then separated to wash the organic layer withwater. These washing operations were repeated for five times. Theobtained organic layer was concentrated, resulting in 23.89 parts of thecompound (F).

MS (mass spectroscopy): 340.1 (molecular ion peak)

Example 5 Synthesis of a Salt Represented by the Formula (II-1)

The salt represented by the formula (II-1-1) was synthesized accordingto the method described in JP 2008-127367A.

10.0 parts of the salt represented by the formula (II-1-1) and 60.00parts of acetonitrile were charged, and stirred for 30 minutes at 40°C., 4.44 parts of the compound represented by the formula (II-1-2) wasadded thereto. The resultant was stirred for 1 hour at 50° C. to obtainthe solution containing the compound represented by the formula(II-1-3). To the obtained solution, 2.63 parts of the compoundrepresented by the formula (II-1-4) was added, and stirred for 1 hour at23° C. To the obtained reacted mass, 80 parts of chloroform and 30 partsof ion-exchanged water were added, stirred, and separated to obtain anorganic layer. The obtained organic layer was washed with water for fivetimes. To the obtained organic layer, 1 part of activated carbon wasadded, and the mixture was stirred for 30 minutes at 23° C. andfiltrated. The filtrate was concentrated to obtain a concentrate, tothis concentrate, 25 parts of acetonitrile was added to dissolve, andthe obtained mixture was concentrated. To the obtained residue, 30 partsof tert-butyl methyl ether was added, stirred for 30 minutes, filtrateto obtain 4.48 parts of the salt represented by the formula (II-1).

Identification of the salt represented by the formula (II-1):

MS (ESI (+) Spectrum): M⁺ 263.1

MS (ESI (−) Spectrum): M⁻ 272.0

Synthetic Example of the Resin

The monomers used the synthesis of the resin are shown below.

These monomers are referred to as “monomer (a1-1-1)” to “monomer (F)”.

Synthetic Example 6 Synthesis of Resin A1-1

Monomer (B) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 77% yield ofpolymer having a weight average molecular weight of about 18000. Thispolymer, which had the structural units of the following formula, wasreferred to Resin A1-1.

Synthetic Example 7 Synthesis of Resin A1-2

Monomer (A) and monomer (C) were mixed together with a mole ratio ofMonomer (A):monomer (C)=90:10, and dioxane was added thereto in anamount equal to 1.5 times by weight of the total amount of monomers toobtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 72° C. After that, the obtained reacted mixture waspoured into a large amount of n-heptane to precipitate a resin. Theobtained resin was filtrated, resulting in a 70% yield of copolymerhaving a weight average molecular weight of about 13000. This copolymer,which had the structural units of the following formula, was referred toResin A1-2.

Synthetic Example 8 Synthesis of Resin A1-3

Monomer (E) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 73% yield ofpolymer having a weight average molecular weight of about 19000. Thispolymer, which had the structural units of the following formula, wasreferred to Resin A1-3.

Synthetic Example 9 Synthesis of Resin A1-4

Monomer (F) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 76% yield ofpolymer having a weight average molecular weight of about 18000. Thispolymer, which had the structural units of the following formula, wasreferred to Resin A1-4.

Synthetic Example 10 Synthesis of Resin A2-1

Monomer (a1-1-3), monomer (a1-2-3), monomer (a2-1-1), monomer (a3-1-1)and monomer (a3-2-3) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 73° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water (4:1) in largeamounts to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a large amount of a mixture of methanoland water to precipitate a resin. The obtained resin was filtrated.These operations were repeated two times for purification, resulting in65% yield of copolymer having a weight average molecular weight of about8100. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-1.

Synthetic Example 11 Synthesis of Resin A2-2

Monomer (a1-1-2), monomer (a1-2-3), monomer (a2-1-1), monomer (a3-1-1)and monomer (a3-2-3) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 73° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water (4:1) in largeamounts to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a large amount of a mixture of methanoland water to precipitate a resin. The obtained resin was filtrated.These operations were repeated two times for purification, resulting in68% yield of copolymer having a weight average molecular weight of about7800. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-2.

Synthetic Example 12 Synthesis of Resin A2-3

Monomer (a1-1-2), monomer (a2-1-1) and monomer (a3-1-1) were mixed withmolar ratio 50:25:25, and dioxane was added thereto in an amount equalto 1.5 weight times of the total amount of monomers.Azobisisobutyronitrile and azobis(2,4-dimethyl valeronitrile) was addedas an initiator thereto in an amount of 1 mol % and 3 mol % respectivelywith respect to the entire amount of monomers, and the resultant mixturewas heated for about 8 hours at 80° C. After that, the reaction solutionwas poured into a mixture of methanol and ion-exchanged water (4:1) inlarge amounts to precipitate a resin. The obtained resin was filtrated.Thus obtained resin was dissolved in another dioxane to obtain asolution, and the solution was poured into a large amount of a mixtureof methanol and water to precipitate a resin. The obtained resin wasfiltrated. These operations were repeated three times for purification,resulting in 60% yield of copolymer having a weight average molecularweight of about 9200. This copolymer, which had the structural unitsderived from the monomers of the following formulae, was designatedResin A2-3.

Synthetic Example 13 Synthesis of Resin A2-4

Monomer (a1-1-2), monomer (a1-2-3), monomer (a2-1-1), monomer (a3-2-3)and monomer (a3-1-1) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 75° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water (4:1) in largeamounts to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a large amount of a mixture of methanoland water to precipitate a resin. The obtained resin was filtrated.These operations were repeated two times for purification, resulting in78% yield of copolymer having a weight average molecular weight of about7200. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-4.

Synthetic Example 14 Synthesis of Resin A2-5

Monomer (a1-1-2), monomer (a1-5-1), monomer (a2-1-1), monomer (a3-2-3)and monomer (a3-1-1) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 75° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water in large amounts toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times for purification, resulting in 78%yield of copolymer having a weight average molecular weight of about7200. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-5.

Synthetic Example 15 Synthesis of Resin X1

Monomer (a1-1-1), monomer (a3-1-1) and monomer (a2-1-1) were mixed withmolar ratio 35:45:20, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 1.0 mol %and 3.0 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a mixture ofa large amount of methanol and water to precipitate a resin. Theobtained resin was filtrated. Thus obtained resin was dissolved inanother dioxane to obtain a solution, and the solution was poured into amixture of methanol and water to precipitate a resin. The obtained resinwas filtrated. These operations were repeated 2 times for purification,resulting in a 75% yield of copolymer having a weight average molecularweight of about 7000. This copolymer, which had the structural units ofthe following formula, was referred to Resin X1.

Synthetic Example 16 Synthesis of Resin X2

Monomer (D) and monomer (a1-1-1) were mixed with molar ratio=80:20, anddioxane was added thereto in an amount equal to 1.5 times by weight ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was addedas an initiator to obtain a solution in an amount of 0.5 mol % and 1.5mol % respectively with respect to the entire amount of monomers, andthe resultant mixture was heated for about 5 hours at 70° C. After that,the obtained reacted mixture was poured into a mixture of a large amountof methanol and water to precipitate a resin. The obtained resin wasfiltrated. Thus obtained resin was dissolved in another dioxane toobtain a solution, and the solution was poured into a mixture ofmethanol and ion-exchanged water to precipitate a resin. The obtainedresin was filtrated. These operations were repeated 2 times, resultingin a 70% yield of copolymer having a weight average molecular weight ofabout 28000. This copolymer, which had the structural units of thefollowing formula, was referred to Resin X2.

(Preparing Resist Composition)

Resist compositions were prepared by mixing and dissolving each of thecomponents shown in Table 1, and then filtrating through a fluororesinfilter having 0.2 μm pore diameter.

TABLE 1 (Unit: parts) Basic BP/PEB Resin Acid Generator Compound (° C.)Ex. 1 A1-1/A2-1 = 0.7/10 II-1/B1 = 0.30/0.70 — 95/85 2 A1-1/A2-2 =0.7/10 II-1/B1 = 0.30/0.70 — 110/105 3 A1-1/A2-3 = 0.7/10 II-1/B1 =0.30/0.70 — 110/105 4 A1-2/A2-1 = 0.7/10 II-1/B1 = 0.30/0.70 — 95/85 5A1-2/A2-2 = 0.7/10 II-1/B1 = 0.30/0.70 — 110/105 6 A1-2/A2-3 = 0.7/10II-1/B1 = 0.30/0.70 — 110/105 7 A1-2/X1 = 0.3/10 II-1/B1 = 0.30/0.70 C1= 0.07 110/105 8 A1-2/X1 = 0.3/10 II-1/B2/B3 = 0.30/1.0/0.1 C1 = 0.07110/105 9 A1-1/A2-4 = 0.7/10 II-1/B1 = 0.30/0.70 — 110/105 10  A1-1/A2-5= 0.7/10 II-1/B1 = 0.30/0.70 — 110/105 11  A1-3/A2-5 = 0.7/10 II-1/B1 =0.30/0.70 — 110/105 12  A1-4/A2-5 = 0.7/10 II-1/B1 = 0.30/0.70 — 110/105Comparative Ex. 1 X2/X1 = 0.3/10 B2/B3 = 1.0/0.1 C1 = 0.07 110/105

<Resin>

Resins Prepared by the Synthetic Examples

<Acid Generator>

B1: this was prepared by a method according to the method described inthe Examples of JP2010-152341A

B2: this was prepared by a method according to the method described inthe Examples of WO2008/99869 and JP2010-26478A

B3: this was prepared by a method according to the method described inthe Examples of JP2005-221721A

<Basic Compound: Qencher>

C1: 2,6-diisopropylaniline (obtained from Tokyo Chemical Industry Co.,LTD)

<Solvent of Resist Composition>

Propylene glycol monomethyl ether acetate 265 parts  Propylene glycolmonomethyl ether 20 parts 2-Heptanone 20 parts γ-butyrolactone 3.5parts 

(Producing Resist Pattern)

A composition for an organic antireflective film (“ARC-29”, by NissanChemical Co. Ltd.) was applied onto 12-inch silicon wafers and baked for60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

The above resist compositions were then applied thereon by spin coatingso that the thickness of the resulting film became 85 nm after drying.

The obtained wafers were then pre-baked for 60 sec on a direct hot plateat the temperatures given in the “PB” column in Table 1 to obtain acomposition layer.

Line and space patterns were then exposed through stepwise changes inexposure quantity using an ArF excimer stepper for immersion lithography(“XT:1900Gi” by ASML Ltd.: NA=1.35, ¾ Annular, X-Y deflection), on thewafers on which the composition layer thus been formed. The ultrapurewater was used for medium of immersion.

After the exposure, post-exposure baking was carried out by 60 secondsat the temperatures given in the “PEB” column in Table 1.

Then, puddle development was carried out with 2.38 wt %tetramethylammonium hydroxide aqueous solution for 60 seconds to obtaina resist pattern.

Effective sensitivity was represented as the exposure amount at which a50 nm line and space pattern resolved to 1:1 with the each resist film.

(Exposure Margin Evaluation (EL))

Exposure margin was evaluated from a graph in which the horizontal axiscorresponds to the exposure amount within the range of an effectivesensitivity±10%, and the vertical axis corresponds to the a line widthof 50 nm-width of line pattern at its amount. In this evaluation,

a double circle was given when absolute value of the slope of theregression line obtained from the above plot was 1.1 nm/(mJ/cm²) orless;

a circle was given when absolute value of the slope thereof was 1.5nm/(mJ/cm²) or less, and more than 1.1 nm/(mJ/cm²);

a cross was given when absolute value of a slope thereof was more than1.5 nm/(mJ/cm²).

(Evaluation of Defects)

The above resist compositions were applied on each of the12-inch-silicon wafers by spin coating so that the thickness of theresulting film became 150 nm after drying.

The obtained wafers were then pre-baked for 60 seconds on a direct hotplate at the temperatures given in the “PB” column in Table 1 to obtaina composition layer.

The thus obtained wafers with the produced composition layers wererinsed with water for 60 seconds using a developing apparatus (ACT-12,Tokyo electron Co. Ltd.).

Thereafter, the number of defects was counted using a defect inspectionapparatus (KLA-2360, KLA-Tencor Co. Ltd.)

Table 2 illustrates the results thereof.

TABLE 2 Ex. EL Defects 1 ∘ (1.14) 190 2 ∘ ∘(1.06) 220 3 ∘ (1.19) 280 4∘∘ (1.06) 200 5 ∘∘ (1.01) 220 6 ∘∘ (1.10) 310 7 ∘∘ (1.09) 410 8 ∘ (1.34)530 9 ∘∘ (1.05) 180 10  ∘∘ (1.03) 160 11  ∘∘ (1.07) 130 12  ∘∘ (1.05)150 Com. x (1.57) 720 Ex. 1

According to the present resist composition, it is possible to achieveexcellent EL at producing the resist pattern. Therefore, the presentresist composition can be used for semiconductor microfabrication.

1. A resist composition comprising a resin having a structural unitrepresented by the formula a resin being insoluble or poorly soluble inalkali aqueous solution, but becoming soluble in an alkali aqueoussolution by the action of an acid and not including the structural unitrepresented by the formula (I), and an acid generator represented by theformula (II),

wherein R¹ represents a hydrogen atom or a methyl group; A¹ represents aC₁ to C₆ alkanediyl group; R² represents a C₁ to C₁₀ hydrocarbon grouphaving a fluorine atom;

wherein R^(b1) and R^(b2) independently represent a fluorine atom or aC₁ to C₆ perfluoroalkyl group; L^(b1) represents a C₁ to C₁₇ divalentsaturated hydrocarbon group, one or more —CH₂— contained in thesaturated hydrocarbon group may be replaced by —O— or —CO—; ring W^(b1)represents a C₂ to C₃₆ heterocycle; R^(b3) represents a hydrogen atom ora C₁ to C₁₂ hydrocarbon group, one or more —CH₂— contained in thehydrocarbon group may be replaced by —O— or —CO—; R^(b4) in eachoccurrence independently represent a C₁ to C₆ hydrocarbon group, one ormore —CH₂— contained in the hydrocarbon group may be replaced by —O— or—CO—; m represents an integer of 0 to 6; and Z¹⁺ represents an organiccation.
 2. The resist composition according to claim 1, wherein A¹ inthe formula (I) is an ethylene group.
 3. The resist compositionaccording to claim 1, wherein R² in the formula (I) is a C₁ to C₆fluorinated alkyl group.
 4. The resist composition according to claim 1,wherein L^(b1) is a group represented by formula (L1-1)

wherein L^(b2) represents a single bond or a C₁ to C₁₅ divalentsaturated hydrocarbon group and * represent a bond to the carbon atom of—C(R^(b1))(R^(b2))—.
 5. The resist composition according to claim 1,wherein Z¹⁺ is a triaryl sulfonium cation.
 6. The resist compositionaccording to claim 1, which further comprises a solvent.
 7. A method forproducing a resist pattern comprising steps of; (1) applying the resistcomposition of claim 1 onto a substrate; (2) drying the appliedcomposition to form a composition layer; (3) exposing the compositionlayer; (4) heating the exposed composition layer, and (5) developing theheated composition layer.